Supply pumping is addressed at the power supply. The SMPS400 and SMPS1200 units have synchronous rectification.

When you have a patent that improves on or adds to an existing design but which is still covered by one or more of the claims of the older patent, you still owe royalties to the owner of the original design. As it happens this is not the case for Ncore. It is a self-oscillating amplifier with global feedback but the actual circuit no longer fits any of the claims of the original UcD patent.

The NC1200 is just the first Ncore module and it's quite specifically targeted at VARs (that's the correct term for "OEM customers"). A module for the DIY market is in the planning stage. Nothing is very concrete yet, apart from that it will be très chique and reasonably powered. I think this might be the right moment for you guys to chip in with feature or spec suggestions. I can't guarantee we can do all of it but definitely every idea will be considered. What probably won't happen is a whole range of DIY Ncore modules because we've outgrown ourselves a bit so let's make this thing one that most people will be happy with.

The NC1200 is just the first Ncore module and it's quite specifically targeted at VARs (that's the correct term for "OEM customers"). A module for the DIY market is in the planning stage. Nothing is very concrete yet, apart from that it will be très chique and reasonably powered. I think this might be the right moment for you guys to chip in with feature or spec suggestions. I can't guarantee we can do all of it but definitely every idea will be considered. What probably won't happen is a whole range of DIY Ncore modules because we've outgrown ourselves a bit so let's make this thing one that most people will be happy with.

Thank you for the explanation, it makes sense. The AB amplifier I used actually doesn't have a current limiter in the traditional sense, it just keeps pumping current until a slow blow fuse dies and its available output current is very high. The NC1200 with 38A of available current should actually work in most cases since the load impedance is never less than 1 Ohm.

@Javin,
If the analyser had two low-distortion sine oscillators and two notch filters I could do low-level IMD plots as well but now I have to use the AD/DA path. As you can see from the grey plots even at high levels the converters pretty much dominate the result so all I could do was to crank up the level until something showed up that was caused by the amp.

You can do an estimate though: because the loop gain is more or less constant up to 20kHz, IMD and THD behave very similarly and furthermore readings will be largely independent of frequency. Under these circumstances, mix products of a 1:1 IMD test will have about the same amplitude as the HD products of a single tone test. If you mix 18.5k and 19.5k, the 2nd order mix product is at 1kHz, the 3rd at 17.5 (and 20.5), the 4th at 2kHz, the 5th at 16.5kHz etc.
This is only conditionally true (only if you don't get thermal modulation effects or slew related distortion for instance) but it holds pretty well for UcD and Ncore.
From the THD FFT plots at 1W you can then estimate that IMD levels will be similar, that is around -110...-120dB depending on the load.
Anyhow, low level IMD does not do anything crazy. There are a variety of fields in audio where people postulate fancy low-level IMD effects that fail to show up with single tones, but I've yet to see that happen in reality. IMD is mostly interesting to characterize performance at high power levels.

@Roberto, the test was done with the unregulated SMPS1200. You can see this from the fact that:
1) 2ohm clipping power isn't four times 8 ohm clipping power
2) clipping power is lower at 100Hz than at 1kHz.
If the power supply were regulated the tail end of the THD plots would overlap exactly and power levels would scale exactly with load impedance. There's something like 10Vpp ripple on the supply at 1200W.

3 questions What is the amount of 2nd and 3rd Harm distortion?

Are the higher harmonic distortions at low levels relative to 2nd and 3rd harmonic?

Do the distortion components decrease in a linear fashion as output is decreased?

Hi Bruno, my premise:it is clear that I do not know your new amp. I like to argue with you on the measures (they are public), thus affecting the community. I think a better fft, can show much more and even that sound can have this amp, or reacts to the PSU as well to the harmonic content (very important to understand (what is not understood by many measures have published). Also , sorry if I insist on thd vs. Power @ 2-4-8R. yes, at total square wave change But if you look at the percentage of modulation (420W 4R), this is repeated in a theoretical power 2R and 8R.
this can not be in reality. (the same percentage of PWM but with different voltage rails, producing different power), of course.
It seems that there is a pre-clip or psu is not smps1200. Also your fft @ 1w, 100hz peak show very low. I think that at 30w fft can clarify a lot about this new amp. (x-axis with obvious than 20kHz), good is fosc/10 Min.
One curiosity, i see a link on your output filter. you can simple explain this?